1 files changed, 23 insertions, 3 deletions
diff --git a/contrib/llvm/lib/Target/Lanai/LanaiISelDAGToDAG.cpp b/contrib/llvm/lib/Target/Lanai/LanaiISelDAGToDAG.cpp
index 29bc6e8..ed0c99a 100644
--- a/contrib/llvm/lib/Target/Lanai/LanaiISelDAGToDAG.cpp
+++ b/contrib/llvm/lib/Target/Lanai/LanaiISelDAGToDAG.cpp
@@ -56,7 +56,7 @@ public:
   }
 
   // Pass Name
-  const char *getPassName() const override {
+  StringRef getPassName() const override {
     return "Lanai DAG->DAG Pattern Instruction Selection";
   }
 
@@ -282,9 +282,29 @@ void LanaiDAGToDAGISel::Select(SDNode *Node) {
     return;
   }
 
-  // Instruction Selection not handled by the auto-generated
-  // tablegen selection should be handled here.
+  // Instruction Selection not handled by the auto-generated tablegen selection
+  // should be handled here.
+  EVT VT = Node->getValueType(0);
   switch (Opcode) {
+  case ISD::Constant:
+    if (VT == MVT::i32) {
+      ConstantSDNode *ConstNode = cast<ConstantSDNode>(Node);
+      // Materialize zero constants as copies from R0. This allows the coalescer
+      // to propagate these into other instructions.
+      if (ConstNode->isNullValue()) {
+        SDValue New = CurDAG->getCopyFromReg(CurDAG->getEntryNode(),
+                                             SDLoc(Node), Lanai::R0, MVT::i32);
+        return ReplaceNode(Node, New.getNode());
+      }
+      // Materialize all ones constants as copies from R1. This allows the
+      // coalescer to propagate these into other instructions.
+      if (ConstNode->isAllOnesValue()) {
+        SDValue New = CurDAG->getCopyFromReg(CurDAG->getEntryNode(),
+                                             SDLoc(Node), Lanai::R1, MVT::i32);
+        return ReplaceNode(Node, New.getNode());
+      }
+    }
+    break;
   case ISD::FrameIndex:
     selectFrameIndex(Node);
     return;